1. Field of the Invention
The present invention relates to a thin film transistor structure, and more particularly, to a thin film transistor structure having an oxide semiconductor layer.
2. Description of Related Art
Regarding a known thin film transistor array substrate, an amorphous silicon (a-Si) thin film transistor or a low temperature poly-crystalline silicon (LTPS) thin film transistor is commonly used as a switch for controlling the electronic signals. Recently, it is found that an oxide semiconductor thin film transistor has higher carrier mobility than the a-Si thin film transistor. Additionally, the oxide semiconductor thin film transistor has better threshold voltage (Vth) uniformity than the LTPS thin film transistor.
Regarding the known oxide semiconductor thin film transistor, the Vth of the oxide semiconductor channel layer would be shifted owing to a light irradiation so that the electric property and the reliability of the oxide semiconductor thin film transistor are affected. Therefore, how to improve the characteristic of the oxide semiconductor thin film transistor has become an important issue.